Beat the pokemon league.
7 island. --> In Sevault canyon on 7 island.
7 island a canyon
go to 7 island
you have to go to island 4 5 6 7 8 or 9
do the elite 4 then go to 7 island and fish near the unkown caves
you get him in 7 island and you must have a venasour
You must beat the seven gym leaders, the elite four, and your rival. Then you have to capture 60 Pokemon to get your Rainbow pass the will allow you to travel to Island 7 in Pokemon FireRed.
in 4-7 islands
I hope this helped
Give it to celio in the one island Pokemon center he will give you a rainbow pass which allows you to access islands 4-7.
== == when you got to 4 5 6 7 AND SO ON Island Ill tell ye'!
explore 7 island . GL !! ^^